Motor vehicle starter with improved starter drive assembly

ABSTRACT

Motor vehicle starter comprising a starter head provided with a pinion ( 1 ), a driver ( 2 ) and a coupling device with a conical clutch for coupling the pinion to the driver ( 2 ), in which the conical clutch comprises a first frustoconical friction surface ( 8 ) fixed to the pinion and a second frustoconical friction surface ( 8 ′) with a shape complementary to the first surface ( 8 ) and fixed to the driver and in which the coupling device comprises on the one hand a hollow-shaped coupling piece having. a bottom extended by an annular skirt directed axially towards one of the elements consisting of pinion and driver and on the other hand axially acting elastic means ( 10 ) bearing on a first stop fixed to the coupling piece for acting on a second stop fixed to one of the elements consisting of pinion and driver. The elastic means comprise axially deformable tongues ( 10   b ) and extend circumferentially.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to motor vehicle starters and moreprecisely to the starter heads which such starters have.

PRIOR ART

As illustrated in FIG. 1, a motor vehicle starter conventionallycomprises a contactor 12 and an electric motor M adapted to drive,directly or indirectly, here via a reduction gear, an output shaft 100,which carries a starter head provided with a pinion 1. The pinion 1 isintended to cooperate with the gearing on the starting ring C of theinternal combustion engine of the motor vehicle. It slides on the outputshaft between an idle position in which it is disengaged with respect tothe said starting ring and a forward position in which it meshes withthe latter whilst being in abutment on a working stop 6.

The contactor 12 extends parallel to the electric motor M above thelatter and comprises a winding 12 a and a solenoid plunger 12 b.

It controls the supply to the electric motor M by moving a movablecontact 13 between an open position and a closed position, the saidcontact 13 being pushed by the said solenoid plunger 12 b able to moveaxially with respect to the electric motor M when the winding 12 a isactivated.

The contactor 12 also controls the movement of the pinion 1. Itssolenoid plunger 12 b is for this purpose connected to the pinion 1 bymechanical means referenced 14 overall.

These mechanical means comprise a control lever in the form of a forkcoupled at its top end to the solenoid plunger 12 b and at its bottomend to a driver also belonging to the starter head. The driver isprovided with a drive socket comprising a groove for receiving the fork.The fork accompanies the starter head to the advanced working positionof the pinion.

The starter head also comprises a free wheel interposed axially betweenthe drive socket and the pinion 1. The drive socket is provided on theinside with helical flutes in engagement in a complementary manner withexternal helical teeth carried locally by the output shaft driven by theelectric motor M when the latter is supplied electrically.

The fork is mounted pivotally between its two ends on a casingcontaining on the inside the mechanical means 14 and carrying the motorM and the contactor 12. The starter head with its pinion 1 is driven ina helical movement when it is moved by the fork in order to come intoengagement with the starting ring.

This is achieved by supplying the winding 12 a following an actuation ofthe ignition key, which moves the solenoid plunger 12 b then attractedin the direction of a fixed core mounted at the end of a support for thewinding 12 a. This support has a U-shaped cross-section for housing thewinding 12 a and therefore comprises a bottom constituting a bearing 12c. The plunger 12 b is therefore intended to move between an idleposition and a contacting position on which it is in abutment on thefixed core; this position of closure of the magnetic circuit takingplace after closure of the moving contact 13 and therefore of theelectrical circuit.

The mechanical means also comprise a return spring mounted around theplunger 12 b in order to return the latter into the idle position, acutoff spring associated with the movable contact 13 in order to returnthe latter into the open position and a spring 15, known as atooth-against-tooth spring, housed inside the plunger 12 b and inengagement with a first rod connected by a spindle to the top end of thefork for coupling the latter to the plunger 12 b. This spring 15 hasgreater stiffness than the return spring.

The fork is therefore interposed at its top end between the plunger 12 band the spindle. The first rod is mounted inside a blind hole in theplunger 12 b. The plunger 12 b is intended, after a given travel, tocome into engagement with a second rod fixed to the moving contact 13and mounted so as to slide inside the fixed core. In the closed positionthe contact 13 cooperates with a fixed contact, in the form of studsconnected respectively to the positive terminal of the battery and tothe electric motor M, thus enabling the electric motor to be supplied.

The studs are fixed to the contactor closure cap made from insulatingmaterial.

All these elements are shown in FIG. 1 and have not all been referencedfor reasons of simplicity.

The pinion 1 can therefore come into engagement with the ring C, that isto say come into the position of meshing with the ring C, before themoving contact is closed.

Usually the pinion 1 comes axially into abutment contact with teeth onthe ring C before entering the latter.

Thus the mechanical means 14 comprise in particular the spring 15, whichis mechanically interposed between the solenoid plunger 12 b and thepinion 1 and which enables the solenoid plunger 12 b to continue itstravel in order, before its contact with the fixed core, to put themoving contact in the closed position, even if the pinion 1 is locked inabutment against the teeth on the ring of the thermal engine in aposition in which it is not meshing with this ring.

As is known, the free wheel, interposed between the pinion 1 and thesocket of the starter head, has the main function of, when the internalcombustion engine of the vehicle starts, preventing the pinion 1 fromdriving the electric motor at an excessively high speed liable to damagethe latter.

The rollers which the free wheel have are each subjected to the actionof a circumferentially acting spring so that this damps the abruptvibrations of the torque transmitted between the driving socket and thepinion 1.

For the purpose of reducing the bulk, weight and cost of the free wheelcompared with its usage, it was proposed in the document FR-A-2 772 433to involve a coupling device with a clutch of the conical type betweenthe pinion and the driver in order to couple the pinion to the starterhead.

In practice, the pinion and the driver each carry for fixingrespectively a first frustoconical friction surface and a secondfrustoconical friction surface. These coaxial friction surfaces havecomplementary shapes, one of the frustoconical friction surfacesentering inside the other frustoconical friction surface, referred to asthe external surface. These surfaces are forced in contact with eachother, with a force with a predetermined value, by means ofaxially-acting elastic means bearing in a first embodiment (FIGS. 3 and4) on a first stop fixed to the free end of a skirt belonging to onepiece, referred for convenience as the coupling piece, annular in shapefor acting on a second stop fixed to the driver so that the driver canslide in rotation with respect to the pinion of the starter head whenthe speed of rotation of the pinion is greater than that of the driver.In a variant in a second embodiment (FIGS. 2 and 5), the elastic meansbear on a first stop fixed to the coupling piece crimped to a ferrulebelonging to the driver for acting on a second stop fixed to the pinion.

The mean diameter of the friction surfaces is substantially equal to thediameter of the pitch circle of the teeth of the starter head pinion. Inpractice the coupling piece consists of a starter head cap having at itsexternal periphery an annular skirt directed axially towards the driverwhilst being cylindrical in shape and axially oriented. This cap has abottom which, in the first embodiment, is axial abutment on a protrusionon an axial extension of the pinion. In the second embodiment theaxially-acting elastic means are interposed between the bottom of thecoupling piece and the axial extension of the pinion.

The elastic means consist in one embodiment of a coiled spring and inanother embodiment of a corrugated ring.

These provisions give satisfaction, but nevertheless it may bedesirable, in a simple and economical fashion, to increase still furtherthe effectiveness and reliability in operation of the coupling devicewith conical clutch.

The object of the present invention is to meet this requirement.

OBJECT OF THE INVENTION

According to the invention a starter of the above-mentioned type ischaracterised in that the elastic means comprise tongues which areelastically deformable axially and in that the tongues extendcircumferentially and axially in the same direction.

By virtue of the invention, the force exerted by the elastic means isbetter controlled so that the effectiveness and reliability of thecoupling device are increased since the elastic tongues generate a moreconstant force as a function of a wearing travel than that generated byan elastic ring of the corrugated type.

This is because, with a corrugated ring, the axial force varies rapidlyaccording to the wearing travel so that the force generated by this typeof ring is great at the start of the service life of the starter headand then decreases subsequently. More precisely the elastic means aremounted under prestressing so as to create, at the frustoconicalfriction surfaces of the conical clutch, a friction torque greater thanthe screwing torque of the driver on the flutes of the output shaft ofthe starter so that it will be sought to have a minimum force at the endof wear on the starter which provides this condition. With a corrugatedring the force must therefore be great at the start of the life of thestarter head in order to achieve this condition at the end of wear. Thishigh force is a nuisance when the motor vehicle engine starts and drivesthe electric motor of the starter since a high residual torque istransmitted from the pinion to this electric motor. A high value of thisresidual torque presents a risk of damage to the electric motor of thestarter by overspeeding.

With this type of corrugated ring a risk is taken from the point of viewof reliability of the starter and from the point of view of the noisegenerated by the overspeeding of the electric motor of the starter.

By virtue of the tongues according to the invention this drawback is notfound since the variations in the forces exerted by these tongues on theconical clutch at the start and end of the life of the starter are lessgreat.

This solution according to the invention increases the service life andreliability of the starter, whilst making it less noisy in overspeed.

With a helical spring it is possible to obtain less great variations inforce provided that the axial length of it is increased, which resultsin increasing the axial length of the starter head.

By virtue of the tongues according to the invention a solution isobtained which is axially compact.

The elastic tongues have a reduced axial bulk and are curved in oneembodiment axially so that, after assembly, the bending forces bring thefriction surfaces in contact with each other.

By acting on the circumferential length and on the thickness of thetongues, the load exerted by the latter is controlled. The tonguesbelong to an elastic area of the axially acting elastic means.

This elastic area is connected to an area for stopping the starter heador pinion in translation, coupled to the skirt of the coupling piece.This stop area is in contact with the stop concerned and is offsetaxially with respect to the free end of the tongues.

In one embodiment it is in the form of an annular cap fixed for exampleby crimping or clipping to the skirt having for this purpose aprotuberance or a groove. In a variant the stop area is reduced to asimple ring.

This ring is, in one embodiment, open for example radially so that itbehaves like a circlip mounted in a groove in the skirt.

The flank of the groove furthest away from the second stop constitutesthe first stop.

This solution is simple and economical since firstly the groove is easyto produce, for example by turning, and secondly the number of parts tobe assembled in the end is at a minimum; the elastic means finally lockthe assembly of the pinion with the driver each constituting asub-assembly.

In a variant the first stop belongs to a piece projecting radiallytowards the inside and attached for example by welding, adhesive bondingor crimping to the free end of the skirt.

In a variant the ring is closed and a mounting of the bayonet type actsfor mounting it on the skirt.

For example, the ring has at its external periphery projecting radiallugs engaging in passages opening out on the one hand at the free end ofthe skirt and on the other hand in the groove.

The lugs are engaged in the passage and then a rotation of the lugs inthe groove is next effected.

In a variant, when the first stop extends in radial projection towardsthe inside, it is divided into annular sectors in order to producepassages, the ring then having at its external periphery scallops forthe annular sectors to pass and allowing a rotation of the ring in orderto bring the external periphery thereof, in the form of lugs, in contactwith the first stop; these sectors advantageously comprise hollows forreceiving the lugs and locking the ring with respect to rotation.

Naturally, in a variant, the elastic means are first put in place andthen the first stop is next attached.

In one embodiment the tongues are cut circumferentially in the ring.

In a variant the elastic area is surrounded by the ring and is connectedto the internal periphery thereof by locating areas.

The tongues are then produced in the form of arms in the shape of anannular sector, which makes it possible to obtain a greatcircumferential length whilst having an advantageous elasticcharacteristic.

More precisely, according to the circumferential length of the arm andits cross-section, the required force is obtained according to the axialdeflection of the arm.

In one embodiment the circumferentially-oriented arms extendcircumferentially in cantilever on each side of a locating area.

The internal periphery of the ring belonging to the stop area has agreater diameter than the diameter of the external periphery of thearms.

The elastic area is then located below the internal periphery of thestop area.

The elastic means according to the invention can for example beintegrated into the cap in FIG. 5 of the aforementioned document FR A 2772 433. Nevertheless it may be desirable to make the starter head morerobust and to simplify it still further, whilst increasing further thereliability and performance of the starter head.

Thus preferably the elastic means are carried by the skirt of thecoupling piece, which internally carries one of the frustoconicalfriction surfaces. This skirt is, via the bottom of the coupling piece,integral with the pinion/starter head element which is associated withthe friction surface carried internally by the skirt, so that the meandiameter of contact of the first frustoconical friction surface with thesecond frustoconical friction surface is greater than the diameter ofthe pitch circle of the teeth of the pinion.

Advantageously the said mean diameter is greater than the diameter ofthe tip circle of the teeth on the pinion.

This mean diameter is, in the event of overspeeding of the pinion withrespect to the driver, a mean friction diameter. The conical clutchaccording to the invention is in a reliable manner locked when theelectric motor of the starter drives the internal combustion engine ofthe vehicle via the starting ring and is adapted to be released when theinternal combustion engine drives the pinion at a higher rotation speed(overspeeding) than that of the driver.

By virtue of these provisions the efficacy and reliability of thestarter head are increased since the mean diameter of the first orsecond frustoconical friction surface is greater because thissurface-belongs to the skirt of the coupling piece located on a largerdiameter than the diameter of the tip circle of the pinion. In this waythe mean diameter of the first frustoconical friction surface isincreased with respect to the diameter of the flutes on the output shaftof the starter carrying the driver. Naturally the mean diameter of thesecond frustoconical friction surface is also increased because the twofrustoconical friction surfaces are coaxial and complementary, thesecond surface entering inside the first surface. These twofrustoconical surfaces have the same cone angle.

Thus, by virtue of the invention, for a given diametral size of thestarter head, the first frustoconical friction surface and the secondfrustoconical friction surface will therefore each have the largestpossible mean friction diameter.

It will also be appreciated that the ferrules in FIGS. 3 and 5 in thedocument FR A 2 772 433 are omitted so that the starter head issimplified and is more robust. The pinion is also simplified.

In general terms the integration of the coupling piece in the pinion ordriver makes it possible to reduce the number of parts to be assembledin the end, the elastic means locking the whole.

Advantageously one of the frustoconical friction surfaces is longeraxially than the other frustoconical friction surface and completelysurrounds it, which further reduces the axial size of the starter head.

In all cases the coupling piece, by means of its skirt and also itsbottom integral in one embodiment in a sealed manner with a pinion,protects the frustoconical friction surfaces and prevents these frombeing soiled, for example by oil and water.

The functioning of the starter head is therefore reliable and it has along service life.

The fact that the coupling piece is for example integral with the pinionreduces the axial size of the starter head because in particular thebottom of the coupling piece does not extend so as to project and alsosimplifies the assembly of the starter head.

The starter head and the coupling piece or the pinion and the couplingpiece constitute a sub-assembly which can be handled and transported andis captive. This sub-assembly is easy to assembly with the secondsub-assembly.

In addition it is possible to produce each of these subassemblies in asingle piece or in several pieces preferably from a different materialadapted to the function to be performed.

It will also be appreciated that the weight and cost of the starter headare reduced.

According to one characteristic the second stop surface is fixed to atransverse shoulder axially delimiting the second or first frustoconicalfriction surface.

This arrangement simplifies the driver or pinion still further andincreases the mechanical strength of these.

This also makes it possible to produce the driver by moulding from aplastics material, which therefore lightens it.

In addition the axially-acting elastic means exert an actionrespectively of the driver and the pinion on a mean diameter close,according to circumstances, to the mean diameter of the second or firstfrustoconical friction surface. In one embodiment the mean diameter ofaction of the axially-acting elastic means is roughly equal to thesmallest diameter of the second frustoconical friction surface.

The action of the axially-acting elastic means on the driver or piniontherefore takes place in a thick area thereof, which is favourable inparticular to their location.

Advantageously the skirt is frustoconical in shape in order to reducefurther the size and weight of the starter head.

In one embodiment the first stop is carried by an extension of thetubular-shaped skirt constituting the free end of the coupling piece.

The tubular extension has an axial length which depends on theapplication and in particular on the axial thickness of theaxially-acting elastic means and makes it possible not to increase theradial size of the starter head whilst facilitating the assembly of thestarter head.

More precisely this tubular extension serves in a simple fashion forfixing a system for holding and closing the complete starter head, thesaid system comprising the first stop and the axially-acting elasticmeans.

In one embodiment the mean diameter for friction and/or contact betweenthe frustoconical friction surfaces is equal to or greater than 75% ofthe diameter of the tubular extension of the skirt.

Other characteristics, aims and advantages of the invention will emergefrom a reading of the detailed description which follows, given withreference to the accompanying figures, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a motor vehicle starter according to the prior art;

FIG. 2 depicts schematically the forces acting within a starteraccording to the invention when the starter drives the internalcombustion engine of the motor vehicle;

FIG. 3 is a view in axial section of the starter head for a firstembodiment according to the invention;

FIG. 4 is a front view of the elastic ring of FIG. 3;

FIG. 5 is a view similar to FIG. 3 for a second example embodimentaccording to the invention;

FIGS. 6 and 7 are views similar to FIGS. 3 and 4 for a third exampleembodiment according to the invention;

FIG. 8 is a view with partial cutaway similar to FIGS. 3 and 5 for afourth example embodiment according to the invention;

FIGS. 9 and 10 are respectively a front and side view of a variantembodiment of FIG. 7.

DESCRIPTION OF PREFERENTIAL EMBODIMENTS OF THE INVENTION

In FIGS. 2 to 8, in order in particular to reduce the number of parts ofthe starter head to be assembled finally and to increase still furtherthe efficacy and reliability of functioning of the starter head, thestarter head of FIG. 1 has, according to one characteristic of theinvention, been replaced by a starter head provided with a pinion 1carrying a first frustoconical friction surface 8 cooperating in acomplementary and coaxial manner with a second frustoconical frictionsurface 8′ carried by the driver 2 in order to form a conical clutch(referenced 7 in FIG. 2), whose mean diameter by which the firstfrustoconical friction surface 8 makes contact with the secondfrustoconical friction surface 8′ is greater than the diameter of thepitch circle of the teeth of the pinion. Here the said mean contactdiameter is greater than the diameter of the tip circle of the teeth ofthe pinion and is, in the event of overspeeding of the pinion withrespect to the driver, a mean friction diameter. The conical clutch anda coupling skirt, annular in shape, belong in the aforementioned mannerto a coupling device (3) acting between the driver 2 and the pinion 1 inorder to couple the pinion to the driver. The coupling skirt is fixed tothe pinion (FIGS. 2, 3, 8) or the driver (FIGS. 5, 6), which reduces thenumber of parts to be assembled in the end and simplifies these. Thesurfaces 8. 8′ have the same cone angle.

According to an important characteristic the skirt carries internallyone of the frustoconical friction surfaces 8, 8′. According to anotherimportant characteristic the skirt carries at its free end axiallyacting elastic means, and this in axial projection with respect to theother surface 8, 8′ not carried by the skirt.

More precisely, the first frustoconical friction surface 8 in FIGS. 2, 3and 8 is carried by the internal periphery of a skirt 1 b of anannular-shaped and hollow coupling piece, whose annular bottom 1 a isfixed to the pinion 1 of the starter head, possibly in several piecesadvantageously made from different materials adapted to their inherentfunction. This bottom has a hole centrally for passage of the outputshaft 100, as can be seen in FIG. 2. The coupling piece is produced forexample economically by pressing a metal sheet. As a variant thecoupling piece is more solid. The skirt 1 b of the coupling piece isdirected axially towards the driver 2. The driver 2 has at its internalperiphery, as in FIG. 1, helical flutes in engagement with helicalflutes carried by the external periphery of the shaft 100. Helicalflutes 9 therefore act in a complementary manner between the shaft 100and the driver 2.

The skirt is connected at one of its axial ends, referred to as thefirst axial end, to the external periphery of the roughly transverselyoriented bottom of the coupling piece. In FIG. 3 the bottom 1 a isfrustoconical in shape, whilst in FIG. 8 it is transverse.

In a first embodiment the skirt is solid, as in FIG. 5, being annular inshape, of axial orientation, at its external periphery. Externally theskirt is therefore cylindrical and internally frustoconical in shape inorder to carry the first frustoconical friction surface.

In another embodiment, as depicted in FIGS. 3 and 8, again for reductionof the weight of the starter head, the skirt is frustoconical in shape,preferably of constant thickness, so that the coupling piece is roughlyin the shape of a bell. This piece is for example made from pressedsheet metal.

According to one characteristic the skirt is extended axially beyond theaxial end of greatest diameter, referred to as the outside diameter, ofthe first frustoconical friction surface 8′ by an axially orientedannular end area (1 c in FIG. 3). The annular area 1 c therefore forms atubular extension of the first surface 8 of the skirt, internallysplayed in shape in the direction of the driver, and extends in axialprojection with respect to the second surface 8′.

This area 1 c, cylindrical in shape, delimits the second axial end ofthe skid, that is to say its free end, and carries a first stop 4 _(l)extending radially towards the inside, that is to say transversely withrespect to the axial symmetry axis X-X of the starter head. The firsttransverse stop 4 _(l) is, in order to reduce the number of parts to beassembled at the end, formed here by means of a groove produced at theinternal periphery of this area 1 c constituting the free end of theskirt and of the coupling piece. It is the transverse flank of thisgroove furthest away from the driver 2 which constitutes the first stop4 ₁.

Axially-acting elastic means 10, advantageously made from spring steel,are carried by the skirt 1 c and bear on the first stop for action on asecond radial, i.e. transverse, stop 4′, fixed to the driver 2, andclamping of the second frustoconical friction surface 8′ fixed to thedriver in contact in a complementary and coaxial manner with the firstfrustoconical friction surface fixed to the skirt and therefore to thepinion of the starter head. The second frustoconical surface 8′ isconvex in shape, whilst the first frustoconical surface 8 is concave inshape. In other words the driver 2 carries a male cone at least partlyentering a female cone carried by the pinion.

As depicted in FIG. 3, the first surface 8 constituting the radiallyexternal friction surface carried by the skirt 1 b completely surroundsthe second radially internal friction surface 8′ carried by the driver2. FIG. 5 illustrates a second embodiment in which it is the driver 2which carries the skirt 2 b, this skirt 2 b then carrying the radiallyexternal friction surface 8′. Thus, according to an advantageousembodiment of the invention, the elastic means 10 are carried by thefree end of the skirt which carries the radially external frictionsurface 8, 8′. This embodiment has the advantage of considerablysimplifying the design of the conical starter head described in thedocument FR 2,772,443 in which the skirt which carries the elastic meanscarries the radially internal friction surface, which requires theproduction of a ferrule.

These surfaces 8, 8′ have a mean diameter greater than the diameter ofthe tip circle of the pinion 1, 10 so that the mean friction or contactmeans of the two surfaces 8, 8′ is greater than the diameter of the tipcircle of the teeth on the pinion. The efficacy and reliability infunctioning of the starter head are therefore increased. The axial sizeis also reduced. In addition the wear on the surfaces is taken up; thefirst surface 8 being in accordance with one characteristic longeraxially than the second surface 8′ so that the driver can move evencloser to the pinion and the axial size of the starter head is furtherreduced. The mean contact and friction diameter between the two frictionsurfaces 8, 8′ is therefore equal to the mean diameter of the secondsurface 8′ having at its axial end adjacent to the elastic means 10 alarger diameter than at its other smaller-diameter axial end. The meandiameter is then situated in the middle of the axial length of thesecond surface 8′; the first surface 8 extending axially on each side ofthe second surface 8′.

The elastic means (or member) 10 also belong to the coupling device 3and more precisely constitute. with the first stop, a system for holdingor retaining and closing the complete starter head.

Therefore a first sub-assembly is first of all manufactured, comprisingthe pinion and the coupling piece provided with the first surface 8 anda second sub-assembly consisting of the driver provided at its externalperiphery with its second surface 8′, and then the driver is movedcloser with respect to the first sub-assembly by slipping the secondsurface into the first surface and finally the elastic means 10 arefitted in order to lock the whole.

These elastic means 10 are located with axial compression, that is tosay under prestressing, between the first stop 4 _(l) and the secondstop 4′ carried here, in order to reduce the axial size of the starterhead still further, by a transverse shoulder 4 _(s) on the driveraxially delimiting, according to one characteristic, the second surface8′ at its largest diameter. The shoulder 4 _(s) is formed by means of anannular removal of material at the external periphery of the body of thedriver, thus making it possible to at least partly house the elasticmeans 10. This removal of material is delimited by the transverseshoulder 4 _(s) and by an annular surface 4″ roughly of axialorientation connected to the internal periphery of the shoulder 4 _(s).The elastic means 10 are here housed entirely in the removal of materialand bear directly on the shoulder 4 _(s) or indirectly on it by means ofa covering. In all cases the stop 4′ is carried by the shoulder 4 _(s).

Naturally, in a variant when problems of radial size are not posed, thefirst stop is carried by an area extending the first surface 8, whichmakes it necessary to increase the radial size of the first stop.

As can be seen in FIG. 4, the elastic means 10 comprise a ring 10 awhich is not closed and therefore open at 10 g. The opening 10 g, hereradial, confers radial elasticity on the ring 10 a, which can then beused as a circlip which is inserted in the aforementioned groove in theextension 1 c, closing the slot 10 g. This ring 10 a is advantageouslymade from spring steel. In a variant the opening 10g is inclined.

In a variant the ring 10 a is closed, as can be seen in FIGS. 7 and 9,and has at its external periphery at least two radial lugs, preferablydiametrically opposed, each adapted to pass through an axial passageopening out in the aforementioned groove comprising the first stop for amounting of the bayonet type.

In a variant the first stop extends in radial projection towards theinside with respect to the internal periphery of the extension over alow height and is attached, preferably in advance, by welding, crimpingor riveting to the extension 1 c. The welding can be of the laser type.The crimping can be carried out in a similar manner to that of FIG. 6when the skirt is solid. In a variant the first stop is a ring which hasin projection radial lugs at its external periphery. These lugs are eachengaged in a complementary manner in a hollow produced at the free endof the skirt. Next the lateral edges of the hollows are crushed in orderto carry out crimping; the skirt advantageously being made from pressedsheet metal. In a variant the lugs can be welded to the lateral edges ofthe hollows.

In a variant the first stop is produced by a folding over of materialradially towards the inside of the free end of the extension 1 c. Thering 10 a is also mounted by closing the slot 10 g.

All combinations are possible, the starter head comprising twosub-assemblies and here a supplementary elastic means 10. This elasticmeans 10 is a member for closing the starter head since it locks the twosub-assemblies 1, 2 of this starter head.

More precisely the elastic means 10 are mounted under prestressingbetween the aforementioned stops and make it possible to keep the secondfrustoconical surface 8′ of the driver under pressure against the firstfrustoconical surface 8 fixed to the pinion 1, 10. It should be notedthat the mean diameter of the first stop, that is to say of the groove,is greater than the mean diameter of the second stop 4′.

The elastic means 10 exert a predetermined force which is substantiallyconstant over time and of a relatively low value which depends on theapplication.

This initial pressure produces a friction torque between the driver andthe pinion which is always, by construction, greater than the torquenecessary for the screwing and forward movement of the starter head onthe shaft 100.

This condition allows the auto-initiation of the movement of the starterhead between its idle position and its advanced position against theworking stop, referenced 6 in FIG. 2, at the start of the phase ofdriving the vehicle engine via the starting ring. When the pinionreaches the stop 6 there is compression of the surfaces 8, 8′ againsteach other with locking.

This movement locking between the pinion and the driver depends inparticular on the angles and diameters of the frustoconical frictionsurfaces.

As can be seen in FIG. 2, during the driving of the internal combustionengine of the motor vehicle by the electric motor of the starter, thetorque Cd—generated by the starter at the output shaft 100 carrying thedriver 2 and converted by the device with helical flutes 9 actingbetween the driver 2 and the shaft 100—creates an axial force Fa.

This force Fa is itself decomposed at the frustoconical frictionsurfaces in order to create a normal contact force Fc, which generates atangential force Ft at the frustoconical surfaces 8, 8′ which is afunction of the coefficient of friction between these surfaces. Thevalue of this force Ft multiplied by the mean radius of contact of thefrustoconical friction surfaces determines the torque Ce transmitted bythe conical clutch 7.

So that the pinion is driven normally without sliding it is necessaryfor the relationship Ce>Cd always to remain true.

All this depends on the application since the coefficient ofproportionality between Cd and Fa depends on the angle of inclination ofthe flutes 9, the mean radius of these flutes and the coefficient ofslip between the output shaft 100 and the driver.

The coefficient of proportionality between Fa and Fc depends on theangle of the cone between the two frustoconical friction surfaces.

The value of Ft is related to Fc and to the coefficient of friction fcbetween the two materials of the frustoconical friction surfaces of theclutch 7. To prevent any jamming it is ensured that the tangentrelationship (a)>f′c, in which a is the value of the half-angle at theapex of the cone of contact between the frustoconical friction surfacesand f′c the coefficient of adhesion.

All these values are calculated according to engineering formulae knownper se and dependent on the applications.

These formulae involve the coefficient of friction between the flutes ofthe shaft and the driver, the mean radius of the flutes, the angle ofthe cone of the surfaces 8, 8′ and the coefficient of friction of these.All this influences the choice of materials of the driver, skirt andpinion.

When the vehicle engine has started the pinion 1 turns more quickly thanthe output shaft 100, which enables the starter head to be unscrewed onthe shaft 100. The axial force previously transmitted disappears and allthat remains is the weak residual torque due to the elastic means 10which is transmitted to the electric motor of the starter. During thisshort overspeed phase the clutch behaves like a freewheel device with arotary movement between the surfaces 8, 8′. The mean diameter of contactbetween the two surfaces 8, 8′ is therefore also a friction diameter inthe case of overspeeding.

The object of the invention is to minimise this residual torque whilstcomplying with the relationship Ce>Cd. Throughout the service life ofthe starter head.

Thus, according to the invention, a starter of the type indicated aboveis characterised in that the elastic means 10 comprise tongues which areelastically deformable axially 10 b and in that the tongues extendcircumferentially.

According to one characteristic of the invention, the tongues 10 bextend axially in the same direction in order to come into abutmentagainst the second stop.

By acting on the circumferential length and on the thickness of thetongues, the axial force developed by them is well controlled.

In FIG. 4 the tongues 10 b are in the form of arms 10 b which extendinside the open ring 10 a. The arms 10 b are in the form of an annularsector extending circumferentially in cantilever on each side of afixing (or anchoring) area 10 d on the ring 10 a. One of the areas 10 dis affected symmetrically by the radial slot 10 g. The two areas 10 dare diametrically opposed so that the arms 10 b extend in reverseorientations axially in the same direction. direction.

The internal periphery of the two arms 10 b associated with the samearea 10 d is in the form of an arc of a circle extending over more than90°. Naturally the number of areas 10 d and arms 10 c can be increased.

The tongues in the form of arms 10 c belong to the axially actingelastic area of the elastic means 10, also comprising the areas 10 d.

This elastic area 10 b extends radially below the ring 10 a, which thushas an inside diameter greater than that of the external periphery ofthe arms 10 b. The elastic means 10 comprise two areas 10 a, 10 b,namely an internal elastic area divided into tongues 10 b, here in theform of arms, circumferentially oriented, and an external area 10 a forstopping the pinion 1 in translation, in the form of a ring 10 a, hereopen and diametrically elastic.

The free ends of the tongues 10 b are offset axially with respect to thestop area according to the application.

The areas 10 d are areas for connection to the ring 10 a.

According to another characteristic these tongues have a zone ofinflection. i.e. an area where there is a change of direction betweentheir anchoring end at the area 10 d and their free end in order betterto control the force which they exert on the second stop 4′. In generalterms the tongues are curved axially in the direction of the driver 2 inorder to keep the surfaces 8, 8′ in contact. In a variant the tonguesare inclined axially, from their end at the anchoring area 10 d, in thedirection of the second stop 4′. In a variant an inclined area connectsthe free end of a tongue to its anchoring end at the area 10 d. Byvirtue of the inclined area creating a fold, the elasticity of thetongue is well controlled and the free end of a tongue can extendparallel to the second stop.

The free end of the tongue can be curved for contact at one point withthe second stop.

The tongues 10 b in general terms are offset axially with respect to thering 10 a, in the direction of the second stop 4′.

This axial offset determines the prestressing of the tongues andtherefore depends on the application.

It will be appreciated that the arms 10 b have a great circumferentiallength, which is favourable for controlling the axial force developed bythese arms.

In a variant the tongues are cut circumferentially in the wider ring 10a.

The coupling piece therefore makes it possible to connect the driver tothe pinion via the frustoconical friction surfaces and replaces the capin FIG. 1. The coupling piece is fixed to the pinion whilst being in asingle piece therewith in FIGS. 2 and 3 or as a variant (FIG. 8)attached fixedly to it. The walls of the coupling piece (its bottom andskirt) are continuous so that the coupling piece is impervious, noopening existing between the bottom of the coupling piece and thepinion. This is favourable for the operating reliability of the starterhead since the surfaces 8, 8′ are not soiled by leakages of oil, wateretc.

The starter head is also simplified since it has no external ferrule,unlike the embodiment in FIGS. 3 and 5 of the document FR-A-2 772 433.

For simplicity in the figures the assembly consisting of pinion andcoupling piece will be referred to as the bell pinion.

Thus in FIGS. 2 and 3 the bell pinion is in a single piece whilst beingmade from a single material or two materials, whilst in a variant (FIG.8) the bell pinion is in two pieces, namely the pinion and the bell;each piece then being chosen optimally according to its function to beperformed.

In the figures the bell pinion comprises on the one hand a toothed partconstituting the pinion 1 and on the other hand a frustoconical part,referenced 1 b in FIG. 3, belonging to the coupling piece.

The toothed part is tubular in shape and has in cross-section the teethwith flanks curved roughly in trapezoidal shape, necessary for meshingwith the starting ring of the internal combustion engine of the motorvehicle. The pinion therefore has teeth defined in a known fashion by atip circle, a pitch circle and a root circle.

It is the internal periphery of the frustoconical part which directly orindirectly constitutes the first frustoconical friction surface. This isbecause the internal periphery of the frustoconical part 1 b can rubdirectly against the second frustoconical friction surface belonging tothe driver or indirectly against the second frustoconical frictionsurface, at least one of the two frustoconical friction surfaces thenbeing provided with a covering such as a friction lining fixed forexample by adhesive bonding. This makes it possible to control inparticular the aforementioned force Ft.

As a friction or rubbing lining it is possible to use a lining of thetype described in the document EP A 0 816 707, comprising a mat offibres impregnated with a thermosetting resin. These fibres are cardedin order to form a card web and advantageously have a length of at least40 mm. Glass is for example incorporated in the mat. For moreinformation reference should be made to this document. With this type oflining remarkable stability of the coefficient of friction of thematerial is obtained, as well as low wear.

The first frustoconical friction surface therefore belongs to theinternal periphery of the skirt of the coupling piece or is attached tothe said internal periphery.

The same applies to the second frustoconical friction surface, which isformed either directly by the external periphery of a frustoconicalsurface belonging to the driver 2 or is attached to the said surface ofthe external periphery.

In all cases at least one of the two frustoconical surfaces 8, 8′ hasgrooves extending from one axial end to the other axial end of thefrustoconical surface concerned, in a rectilinear or curved fashion. Ina variant the grooves extend circumferentially. A network ofcircumferential and rectilinear and/or curved intersecting grooves canbe produced. This network can comprise circumferential grooves connectedto the axial ends of the frustoconical surface concerned by distinctgrooves extending in a rectilinear or curved manner. All combinationsare possible. For example, the grooves are provided at the externalperiphery of the second surface, or as a variant at the internalperiphery of the first surface.

By means of the grooves the dust is discharged and the detachment of thetwo surfaces with respect to each other is assisted, in particular inthe case of overspeeding.

As on the pinions of conventional starter heads, the teeth on thetoothed parts 1 are preferably provided at their free end, on theopposite side to the driver 2, with a bevel for facilitating the entryof the pinion into the starting ring visible at C in FIG. 1.

In these FIGS. 2 and 3 the frustoconical bottom 1 a is roughly oftransverse orientation since it extends in an inclined fashion withrespect to the axial symmetry axis X-X of the starter head visible inFIGS. 3 and 8. This axis is at the same time the axis of symmetry of theshaft 100. In a variant, FIG. 8, the bottom extends perpendicular to theaxis X-X. In fact it is possible to standardise the driver and,according to the radial and axial size of the pinion, incline the bottom1 a more or less or make it transverse. All this depends on theapplication.

Thus in FIG. 3 the pinion 1 has at its end turned towards the driver 2an inclined extension 1 a constituting the bottom of the coupling piecein the form of a bell and connecting the parts 1, 1 b together.

The bell pinion is for example obtained by casting. Advantageously thebell pinion is obtained by sintering whilst being made from one materialor preferably two materials.

The two-material sintering is very advantageous since there is a choicefor the toothed part of a grade of material more specifically adapted tothe requirements of the meshing with the starting ring (mechanicalstrength, resistance to wear, low noise emission etc) whilst thefrustoconical part is specially adapted to the requirements of theclutch 7 (resistance to wear, value of the coefficient of friction etc).

The toothed part 1 is obtained for example by extrusion, sintering,cutting from a bar or pressing. This toothed part 1 is in a variantdistinct from the bell, which has a plate with a central hole forpassage of the shaft 100 and constituting the bottom of the bell. Thisplate 1 a is extended at its external periphery by the frustoconicalskirt 1 b, itself extended by the tubular extension 1 c. The firstfrustoconical surface 8 consists of the internal periphery of the skirt1 b.

In a variant, as can be seen in FIG. 8, the plate 1 a is attached at itsinternal periphery by welding to the pinion having for this purpose atits internal periphery a tubular extension 1 d extending in axialprojection towards the driver and making it possible to centre the plate1 a at its internal periphery. This plate is fixed axially in onedirection by the adjacent axial end of the teeth of the pinion and inthe other direction by the welding carried out at the free end of theextension. The welding is in one embodiment carried out continuously, orin a variant discontinuously. The welding is of the laser type, of thefriction welding type or of the arc welding type.

In a variant the fixing is carried out by crimping, the free end of theaforementioned tubular extension being folded over in contact with theplate 1 a itself in abutment on the teeth of the pinion 1. In this caseuse can be made of complementary connections, for example of thepolygonal type, to lock the plate with respect to rotation. Therotational locking of the bell on the pinion is carried out in generalterms by cooperation of shapes. The teeth on the pinion can be used toeffect this fixing. For example the plate 1 a is dished locally in orderto form at least a projection entering in a complementary manner betweentwo consecutive teeth on the pinion. In a variant the plate is dished inthe opposite direction in order to form at least one hollow in which atleast the end of one tooth on the pinion enters in a complementarymanner, this tooth being enabled to cooperate with the lateral edges ofthe hollow. The number of projections and hollows depends on theapplication.

In a variant it is possible to make connections by shrinking on.

In all cases an axial and rotational immobilisation of the bell withrespect to the pinion, that is to say a fixing, is obtained.

In a variant the pinion 1 is made from sintered material and the bell,made from solid metal, is mounted, by means of its plate, with slightclamping on the projecting tubular extension 1 d of the pinion 1 so asto remain correctly positioned on the pinion during handling of theassembly thus formed before this assembly is passed through a furnacefor sintering of the pinion. During this passage through the furnace themetal of the pinion swells and thus provides, in addition to themetallurgical connections of the sintering, definitive immobilisation ofthese two parts. Aforementioned connections by cooperation of shapes,such as polygonal nesting, can take place in order to contribute to therotational connection between these two parts.

In a variant the bell is also made from sintered material, preferablydifferent from that of the pinion, in order to obtain good frictioncharacteristics. The two parts are then preassembled before passingthrough the sintering furnace. The coefficient of swelling of the pinionis at least as great as that of the bell so as to preserve close contactbetween these two parts and to assist the creation of strongmetallurgical connections. After the sintering a single-piece assemblyis obtained with different mechanical characteristics according to theareas in question.

In one embodiment the toothed part is obtained by two-material sinteringin order to obtain on the one hand good properties of sliding along theshaft 100 and on the other hand good properties for meshing with thestarting ring.

It is possible to conceive that this toothed part may itself be in twopieces, namely an internal sleeve made from material allowing goodsliding along the shaft 100, and a pinion mounted on the externalperiphery of the sleeve and having a material exhibiting good propertiesfor meshing with the starting ring. The tubular extension 1 d thenconstitutes one of the axial ends of the sleeve.

This can be achieved in the same way as with the assembly of the bellwith the pinion. For example, the toothed part is mounted for clampingon the extension 1 d of the sleeve before the operation of sintering atleast one of these pieces. When the two pieces are sintered, thecoefficient of swelling of the sleeve is at least equal to that of thetoothed part. In a variant a connection by shrinking on is effected.

In a variant the sleeve is fixed to the bell whilst being in a singlepiece therewith or fixed to it. The solution with an attached sleeve isadvantageous since, for a given shaft size 100, it is possible tostandardise the sleeve, if necessary with the bell, and adapt the pinionmounted on the external periphery of the sleeve to each application, inparticular with regard to its length. It is also possible to axiallyposition the toothed part as required with respect to the sleeve with agreater axial length than the toothed part.

The bell pinion is therefore in one, two or three pieces. It should benoted that the bottom of the bell is connected to the skirt thereofeither by means of a rounded area or by means of a frustoconical area.

The same reasoning can be made for the driver 2, which is therefore inone or more pieces each made from a different material in order tofulfil its inherent function in an optimum fashion. For example, asdescribed in the document FR A 2 772 433, the driver can have a metallicpiece, such as a ring provided with at least one collar, attached to thebody of the starter head in order to cooperate with the fork of themechanical means 14 in FIG. 1. The aforementioned ring comprises, in oneembodiment, two collars so that it has a U-shaped cross-section forreceiving the fork.

As can be seen in the figures the driver comprises three portions,namely a first portion having at its external periphery the secondfrustoconical surface. This first portion extends in axial and radialprojection with respect to a second portion, constituting the sleeve ofthe driver and having on the inside the helical flutes adapted tocooperate in a complementary manner with the helical flutes on the shaft100. An annular groove for receiving the fork of the mechanical means 14of FIG. 1 is provided at the external periphery of the second portion.This groove, delimited by two transverse flanks adapted to cooperatewith the fork of the means 14, belongs to the third portion of thedriver 2 and is offset axially with respect to the first portion. Thisgroove extends radially above the flutes of the second portion whilstbeing shorter axially. The second frustoconical surface, advantageouslyprovided with grooves in the aforementioned manner, extends in radialprojection with respect to the groove and is connected to the groove viathe removal of material 4′, 4″ effected in the first portion for housingthe elastic means 10. A frustoconical face connects the relevant end ofthe second portion to the smaller-diameter end of the secondfrustoconical surface in order to reduce the quantity of material of thedriver, here made from mouldable plastics material advantageouslyreinforced with fibres. In a variant anti-wear coverings are made on oneof the two flanks delimiting the groove, in particular when the fork ofthe mechanical means 14 is metallic. These coverings consist for exampleof metallic rings fixed by moulding onto the flanks of the groove, or ina variant half-rings or a U-shaped piece fixed by snapping onto theflanks of the groove. In a variant the flank of the groove furthest awayfrom the pinion is formed by means of an attached ring, all combinationsbeing possible. The second friction surface can be formed also by meansof a covering, such as the aforementioned friction lining, so that thebody of the driver and therefore the second portion thereof isadvantageously made from a material having the required qualities forcooperating with the flutes on the shaft 100. The driver 2 as a variantis obtained by sintering from a single material or as a variant severalmaterials like the pinion. It will be appreciated that, when the belland/or the driver are made from sintered material it is possible toincorporate in this the required fillers for obtaining the desiredcoefficient of friction for the surfaces 8, 8′. For example thesesurfaces can contain copper powder, carbon for example in the form ofgraphite, silica and molybdenum.

The fork of the means 14 is advantageously made from plastics materialin order to limit the phenomena of incrustation in the driver and reducenoise. In a variant the groove and therefore the second portion of thedriver can extend radially above the second surface 8′ and the skirt ofthe coupling piece.

Naturally it is possible to reverse the structures, the annular shapedand hollow coupling piece then belonging to the driver 2.

The free end of the skirt 2 b of the coupling piece extends in axialprojection with respect to the first surface 8 and carries the elasticmeans 10.

Thus in FIG. 5 the skirt 2 and the plate 2 a of the coupling piece inthe form of a bell belong to the driver 2, which carries at its externalperiphery a female cone in which a male cone carried by the pinionenters. The second frustoconical friction surface 8′ surrounds the firstfrustoconical friction surface whilst being axially longer than it. Itis the driver 2 which carries the bell provided with an annular skirt 2b directed axially towards the teeth of the pinion. This skirt is ofnon-constant thickness whilst being delimited at its external peripheryby an axially oriented annular wall, that is to say cylindrical, and atits internal periphery by the second concave shaped surface 8′, thefirst complementary surface 8 being convex in shape. The skirt isconnected, by means of the transverse plate 2 a, to the aforementionedsecond portion of the driver 2. The bell belongs to the first portion ofthe driver 2. The mounting groove of the ring in FIGS. 3 and 4 belongsto the free end of the skirt, whilst the removal of material housing theelastic means 10 is formed in a supplementary portion of the pinion 1equivalent to the first portion of the driver of the embodiment in FIGS.3 and 4. It is therefore possible to use the same ring as for FIGS. 3and 5.

It will be noted that the supplementary portion of the pinionconstitutes an extension extending in radial and axial projection withrespect to the teeth of the pinion 1. It is the external periphery ofthis extension which carries the first surface 8, whose mean diameterconstitutes the mean contact diameter of the surfaces 8, 8′. This meandiameter is greater than the diameter of the tip circle of the toothedpart of the pinion 1.

In FIGS. 3 and 5 the smallest diameter of the first surface 8 is greaterthan the diameter of the tip circle of the toothed part of the pinion 1.The extension is here cast in one piece with the pinion 1.

The skirt 2 b is solid so that the groove is produced at the free end ofthe skirt 2 b in the projecting part of the second surface 8′ withrespect to the first surface 8′. The plate 2 a, here transverse or in avariant frustoconical, and the skirt 2 b are in one piece with thedriver 2. In a variant the bell is attached to the driver for example inthe same way as the assembly in FIG. 8. In this case the second portionof the driver has on the inside a projecting tubular extensionshouldered for mounting an axial fixing in one direction of the plate 2a. All the aforementioned forms of assembly are transposable in thisconfiguration mode and vice-versa.

It should be noted that the plate 2 a forms one of the flanks of thereception groove of the fork of the means 14.

Naturally as a variant (FIGS. 6 and 7) the ring 10 a is continuous andis extended at its external periphery by a tubular part 10 f provided atits free end with lugs 10 c folded over in contact with an inclined face2 d belonging to an annular protuberance 2 e which the skirt 2 a has inradial projection at its external periphery. This protuberance isconnected to the transverse face of the free end of the skirt and has acylindrical centring surface 2 f for the tubular part 10 f.

The elastic means therefore comprise an area for stopping the pinion intranslation in the form of an annular cap carried by the skirt.

The transverse face of the free end of the skirt constitutes the firststop.

The inclined face 2 d can be provided with hollows for rotationallylocking the cap by cooperation of the lugs 10 c with the lateral edgesof the hollows. The cap is immobilised axially by means of the face 2 dand the face of the free end of the skirt.

In the preceding figures the axial immobilisation is effected with aslight clearance by mounting of the ring 10 a in the groove.

In a variant a groove is produced in the surface 2 f and the tubularpart 10 f is pressed locally into the groove. The crimping lugs 10 c arethen omitted.

In a variant the tubular part 10 f is pressed in locally by forwardmovement towards the inside and the mounting of the tubular part 10 f onthe surface 2 f is achieved by snapping the pressed areas of the part 10f into the groove of the part 10 f.

In a variant the ring 10 a has axial lugs at its external periphery eachprovided at their free end with a hole for mounting by snapping on acomplementary stud issuing from the external periphery of the skirt. Todo this each hole belongs to an elastic area formed for example by meansof a concertina folding.

In a variant the axial lugs are provided at their free end withelastically deformable inclined projections for forming claws intendedto come into engagement by snapping on with the studs.

In a variant the claws are formed by means of fixing areas 10 d as canbe seen in FIGS. 9 and 10. These claws 10 e then come into engagementelastically with an internal periphery 1 e of the extension 1 c or 2 cof the skirt constituting the free end thereof. FIG. 10 shows in dottedlines part of the extension of 1 c. In this case the ring 10 a is thencontinuous and has four arms 10 b and two fixing areas 10 d as in FIG.7. The areas 10 d are delimited circumferentially at their externalperiphery by two blind slots 110 each connected to a claw 10 e extendingin radial projection with respect to the external periphery of the ring10 a. The height of these claws is here slight. These claws 10 e areconnected to each other by a flat portion 111 delimiting the externalperiphery of a fixing area 10 d.

The claws are each delimited by the edge of a slot 110, a rectilinearportion constituting the external periphery of the claw 10 e and aninclined portion for connecting to the flat portion 111.

Each fixing area 10 d thus has at its external periphery a tongue 112less wide circumferentially than the said area 10 d.

Each tongue 112 has a claw 10 e at each of its ends. The tongues 112 canflex axially.

The outside diameter of the claws 10 e is slightly greater than theinside diameter of the extension 1 c so that, when the elastic means arefitted axially in the extension 1 c, the tongues flex axially so thatthe claws remain in engagement under pressure with the internal bore ofthe internal extension 1 c, as can be seen in FIG. 10. When the elasticmeans 10 are subjected to a force acting in the opposite direction tothat of the fitting in, the elastic means lock by bracing. The tongues112 have roughly the shape of the head of a cat with two ears formed byclaws 10 e.

The groove in FIGS. 3 and 5 can be omitted. In a variant the groove iskept so that the axial locking of the elastic means 10 is improved.

In a variant the groove is replaced by hollows for receiving the claws10 e.

Advantageously the claws 10 e are mounted under pressure in the grooveor the hollows in order to prevent any movement following vibrations.

As is obviously clear from the description and drawings, the torquetransmission capacity of the starter head is increased by virtue of alarge mean friction diameter for a given diametral size. The number ofparts as well as the axial and diametral size of the starter head arealso reduced. A good seal is obtained with regard to splashing of oil orwater directed towards the pinion by virtue of the bell. There is apossibility of choosing different materials, one well suited to themechanical characteristics required by the pinion, the other being welladapted to the requirements of friction and resistance to wear of theconical clutch.

In a variant the cap in FIGS. 6 and 7 can replace the cap in FIG. 5 ofthe document FR-A-2 772 433, which allows a reduction in the number ofparts.

Advantageously use is made of an electronic control device for theelectrical supply to the winding 12 a and the electric motor of thestarter in order to reduce the duration of the “freewheel” operatingphase of the conical clutch and to be independent of the reaction timeof the driver. For example, the electronic device is of the typedescribed in the document FR A 2 795 884 supplying the winding 12 a bymeans of a transistor according to a square-wave voltage of the “PulseWidth Modulation” (PWM) type in French.

More precisely the effective current in the winding 12 a is variedduring the movement of the core 12 b towards its contacting position, inorder to close the moving contact 13 and supply the electric motor M.

During this movement there are adopted:

-   -   a first driving phase with a sufficiently high effective current        to move the core 12 b, then    -   a second driving phase with a weaker effective current,    -   during the second phase, after a predetermined or given time, a        continuous increase in the effective current is implemented.

For more information reference should be made to this document.

By virtue of the electronic device it is possible to choose a less noblefriction material for the friction surfaces 8, 8′ since the overspeedphase and therefore the phase of sliding between the two surfaces isbetter controlled. This makes it possible to reduce costs.

Advantageously, in order to improve the conical-clutch starter head, atorsion damper with circumferentially acting elastic means and/or atorque limiter are in a variant associated with the starter head.

Thus, in a first embodiment, the torsion damper and the torque limiterare associated with the reduction gear with epicyclic train of FIG. 1interposed between the electric motor and the output shaft 100 on whichthe driver 2 is mounted.

For this purpose it is possible to adopt for example the solutiondescribed in the document FR 99 16726 filed on Dec. 30, 1999. The torquelimiter is then interposed axially between the ring of the reductiongear and a plate of a housing inside which the ring is mounted forrotation.

The elastic means then consist of at least one elastically deformabledamper block, being for example made from elastomer, rotationallyconnecting to the housing a disc belonging to the torque limiter. In avariant the starting ring belongs to the secondary mass of a dampingflywheel connected to the gearbox of the motor vehicle. This secondarymass is connected by a torsion damper and a torque limiter to a primaryflywheel connected to the vehicle crankshaft, as described for examplein the document FR A 2 598 475.

In a variant only one of the two torque limiting or torsion dampingdevices is present.

In a variant it is possible to provide the aforementioned two devices.

The presence of a fork is not obligatory. The starter can thus have theconstitution described in the document EP-A-0 867 613 describing asolution with a reduction gear whose output shaft acts on the starterhead.

1. A motor vehicle starter comprising a starter head provided with a pinion , a driver and a coupling device with a conical clutch for coupling the pinion to the driver, the conical clutch comprising a first frustoconical friction surface fixed to the pinion and a second frustoconical friction surface complementary in shape to the first surface and fixed to the driver, the coupling device including a hollow-shaped coupling piece having a bottom and an annular skirt extending from the bottom axially towards one of the pinion and the driver and an axially acting elastic member bearing on a first stop fixed to the skirt of the coupling piece for acting on a second stop fixed to one of the pinion and the driver for biasing the pinion toward the driver, wherein the axially acting elastic member comprises a ring and axially deformable tongues extending from the ring circumferentially, wherein the tongues are bent axially so as to be offset axially with respect to the ring in the direction of the second stop, and wherein the tongues are in the form of arms which extend inside the ring.
 2. The starter according to claim 1, wherein each of the tongues is additionally bent in a zone of inflection spaced from an anchoring end of the tongue.
 3. The starter according to claim 1, wherein each of the tongues has an inclined area connected to a free end of the tongue.
 4. The starter according to claim 1, wherein free ends of the tongues are curved for a contact with the second stop.
 5. The starter according to claim 1, wherein the elastic tongues are connected to an internal periphery of the ring by means of anchoring areas.
 6. The starter according to claim 5, wherein each of the arms of the tongues is in the form of an angular sector extending circumferentially in cantilever on each side of the anchoring area connecting the sector to the ring.
 7. The starter according to claim 6, wherein the ring has a slot so as to form an incomplete ring.
 8. The starter according to claim 7, wherein the slot is a radial slot symmetrically affecting the anchoring area connecting at least one of the tongues to the ring.
 9. The starter according to claim 7, wherein the ring of the axially acting elastic member is in the form of a circlip and is received in a groove produced at the internal periphery of a free end of the skirt.
 10. The starter according to claim 5, wherein the axially acting elastic member has claws intended to come into engagement elastically with an internal periphery of a free end of the skirt of the coupling piece.
 11. The starter according to claim 10, wherein the claws belong to tongues formed at the external periphery of the anchoring areas by means of blind slots, and wherein the claws extend in radial projection with respect to the ring.
 12. The starter according to claim 1, wherein the ring is extended at its external periphery by an axially oriented part in order to form a cap.
 13. The starter according to claim 1, wherein the elastic member is carried by the skirt of the coupling piece and in that the said skirt carries internally one of the first and second surfaces.
 14. The starter according to claim 13, wherein the skirt of the coupling piece is fixed to one of the pinion and starter head and includes the first friction surface associated with the pinion and the second friction surface associated with the starter head.
 15. The starter according to claim 14, wherein a mean diameter of contact of the first surface with the second surface is greater than the diameter of a tip circle of teeth on the pinion.
 16. The starter according to claim 13, wherein the elastic member is carried by a free end of the skirt which carries the radially external friction surface.
 17. The starter according to claim 13, wherein the first or second surface carried by the skirt is longer axially than the other second or first surface.
 18. The starter according to claim 1, wherein the elastic member is carried by a free end of the skirt and in that the elastic means extend in axial projection with respect to the said other second or first surface.
 19. The starter according to claim 18, wherein a largest-diameter axial end of the other surface is delimited by a transverse shoulder carrying the second stop for location with axial compression of the axially acting elastic means between this second stop and the first stop carried by the free end of the skirt of the coupling piece.
 20. The starter according to claim 18, wherein a transverse shoulder is extended at its internal periphery by an annular surface of roughly axial orientation delimiting with the shoulder a removal of material in order to at least partly house the axially acting elastic member.
 21. The starter according to claim 18, wherein the cap is fixed to the free end of the skirt at the external periphery thereof.
 22. The starter according to claim 1, wherein the skirt of the coupling piece is frustoconical in shape.
 23. The starter according to claim 1, wherein at least one of the first and second friction surfaces includes a friction lining.
 24. The starter according to claim 1, wherein the pinion is made as a single piece with the coupling piece roughly in the form of a bell.
 25. The starter according to claim 1, wherein the coupling piece is fixed to the pinion.
 26. The starter according to claim 1, wherein the coupling piece is fixed to the starter head.
 27. The starter according to claim 1, wherein the starter has at least one winding controlling an electric motor and adapted to be supplied electrically by an electronic control device for maneuvering the starter head.
 28. The starter according to claim 1, wherein the tongues are bent axially proximal to anchoring ends thereof. 